SIG SAUER® 80% P320 Completion Jig

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SIG SAUER® 80% P320 Completion Jig

The Sig® P320 is the latest handgun to get the 80%-pistol treatment, allowing builders to fabricate their own factory-compatible Sig Sauer Fire Control Unit -- the modular firearm component of the P320 platform -- with some basic tools and little to no experience required. With a fabricated 80% FCU (called the MUP-1 insert), your homemade P320 can be chambered in three calibers and configured in four sizes with no tools or extra gunsmithing services required.

How the P320 80% Jig Works

First, federal law says it's legal to build a gun at home for person use, from scratch, with no paperwork or FFL required. Since the Sig P320's FCU (which is little more than a stamped and drilled piece of steel) is the only part of the handgun considered a firearm, this is the part you will fabricate by cutting and drilling with the 80% jig. To do that, the P320 jig provides the "template" for completing those steps, which include:

  • Drilling various pin holes
  • Cutting the trigger slot
  • Bending the slide rails
  • Trimming the slide rails

All of these steps are easily completed with hand tools (Dremel and hand drill) as shown below with detailed video instrunctions.

With these fabrication steps completed, your finished Fire Control Unit can accept any of Sig Sauer's various P320 components in all calibers and configurations. Since the FCU is the only part of the gun considered a firearm once machined, you can purchase all other parts -- the barrel, slide, trigger mechanism, and frame, or "grip module" -- with no FFL or paperwork required under federal law. Some states have placed restrictions on these products, detailed below.

What's Included With the P320 80% Jig

  • Jig side plates with pin hole and trigger templates
  • Top plate for bending and trimming the slide rails
  • All required drill bits for various pin holes
  • Detailed instructions for first-time builders

In addition to the finishing jig and 80% FCU insert, each Sig Completion Kit also includes the parts for assembling your finished FCU and building a complete P320-compatible handgun in Full or Carry sizes:

  • The Lower Parts Kit for FCU: Required to assemble the FCU, making it functional. Quality, U.S.-made components.
  • The P320 Modular Build Kit: Slide with night sights, barrel, guide rod/recoil spring assembly, and grip module (frame).
  • Convenient Carry Case: To transport your new shooter to and from the range as soon as you're finished building it.

P320 Jig Kit Features:

  • NO FFL Required
  • Includes factory-compatible 80% FCU
  • Includes all parts required for pistol assembly
  • All components proudly U.S.-made and OEM in quality
  • Just one completed FCU required to build all pistol configurations

Some states have banned 80% lowers and certain firearm parts, or have otherwise restricted the sale and ownership of products we sell. So, be sure to check your local and state laws. We can’t ship our products to certain states. Please check our Shipping & Return Policy before placing an order (see restrictions).

Your new modular pistol build awaits.


DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

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We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.